Rheostat



(No Model.) J B BLOD lRHIEOSTAT- No. 508,674. Patented Nov. 14, 1893.

vUNITED STATES PATENT OFFICE.

JOHN B. BLOOD, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE THOMSON- HOUSTON ELECTRIC COMPANY, OF CONNECTICUT.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 508,67 4, dated November 14, 1893.

Application filed Febr-.lary 23. 1892- Serial No. 422,340- (No model.) l

To all whom it may concern: Movement of the arm H to the right decreases Be it known that I, JOHN B. BLOOD, a citithe resistance of/the circuit while movement zen of the United States, residing at Lynn, to the left cuts in additional resistance, as

countyof Essex, State of Massachusetts, have will be readily understood without further ex- 5 invented a certain new and useful Improveplanation. The contact plates K are of cop- 55 ment in Rheostats, of which the following is per and are supported on an insulating sura SDecitication. face, such as a slab S of slate or porcelain. The objectof the present invention is to ob- Back of this slab upon a suitable support D viate the occurrence of sparking or arcing beis fixed a magnet or system of magnets hav- 1o tween the adjoining` contact plates of rheoing poles P corresponding `generally in num- 6o stats, or other resistance controllers for elecber and position to the intervals between the tric circuits, which arcing, when the potential different contacts K. The poles project difference between the contact plates is rather through the insulating base to within as short high, may become a source of trouble by burna distance as practicable of the gaps between 15 ing the metal and thus preventing free pasthe contact plates, and preferably they are ar- 65 sage of the contact block or brush over the ranged so that each pole is'of opposite poplates. 'Io this endI providea magnet or syslarity to the pole next it in the series. The tem of magnets having poles arranged adjamagnets may be permanent magnets,butpref cent to the successive intervals between the erably are electro-magnets with iron cores 2o contacts so that, when the contact arm leaves wound with coils of wire through which cur- 7o one plate to make contact with the next, it rent is passed from any suitable source. The forms a more or less complete magnetic bridge contact arm has a brush or block B for enbetween the adjacent' magnet poles. In this gaging the different contacts which may be way a strong and intense magnetic field is made of carbon or of metal, and may be y z5 concentrated at the point where the current pressed by a spring C into engagement with 75 vis interrupted which prevents any continued the plates. The arm also has formed on its arcing thereat. The construction of the conouter end or attached to it an iron armature tact arm is not altered, and in fact the only T of such width as to span two of the magnet change in existing constructions is the addipoles. It therefore forms a more orless coml 3o tion of the magnets. With such an arrangeplete magnetic bridge between those poles im- 8o ment it is possible to employ rheostats with mediately adjacent to the arm, and thereby comparatively few divisions,when desired,for gives rise to an intense magnetic field at this though in such an apparatus there would be point which will extinguish any arcs which a large potential difference between adjacent may form upon the passage of the contact 35 contacts yet any arc formed would be extinblock from one plate to another. 8 5 guished without damage. In putting this invention to practical use In the accompanying drawings, Figure l is as many magnet poles maybe provided as may a plan view of the invention,` and Fig. 2 is a prove necessary, butit is not essential to place section on the line :v -cc Fig. I. a pole back of each gap between the contact 4o In the gures Q represents an electric cirplates unless the potential difference between 9o cuit, in which is coupled up any translating such plates is quite high and sufficient to device, such for example, as an electric motor maintain an arc thereat. J shown conventionally in thedrawings. To Vlhat I claim asnew, and desire to secure vary the amount of current owing to the by Letters Patent, is-

45 motor the circuit comprises a resistance R l. The combination of the contacts of are- 95 and a contact or switch arm Il which sweeps sistance controller for electric circuits, with over and engages a series of 'contacts K, conan electro-magnet having a series' of poles nected to successive portions of the resistcorresponding to the intervals between the ance in the ordinary manner, but separatedY contacts and arranged adjacent thereto, each 5o one from another by an insulating interval. such pole being of opposite polarity to that 100 at the next interval, and a movable contact arm adapted to form a magnetic bridge between two adjacent poles as described.

2. The combination of the contacts of a resistance controller for electric circuits, and a magnet having poles separated one from another bysuch contacts and arranged adjacent to the intervals between them, with a contact arm adapted to sweep oversuch contacts and form a part of the magnetic circuit between unlike poles, as described.

3. The combination of the contacts of a resistance controller for electric circuits, with a magnet or system ot' magnets having poles arranged adjacent tothe intervals between such contacts, and a contact arm formingt part JOHN B. BLOOD.

Witnesses:

J oHN T. BRoDEaicK, JOHN W. GIBBONEY. 

